Core Topics in General & Emergency Surgery: Companion to Specialist Surgical Practice (72 page)

Duration of anticoagulation

There remains uncertainty about the optimal duration of anticoagulation following a VTE. Systematic reviews have considered the duration of anticoagulation after an episode of VTE and have reported that, while the risk of recurrent VTE is low should anticoagulant therapy be continued, the risk of bleeding is increased.
93
Short-term anticoagulation (less than 3 months) is associated with a higher risk of recurrence compared with longer-term treatment.
94
Following cessation of oral anticoagulation after a first episode of VTE, the risk of recurrence is 7–12.9% after 1 year and 21.5–22.8% after 5 years.
9,
95

 

At least 3 months of anticoagulant therapy is required after a proximal DVT or PE; 3 months is likely sufficient after a first event if it was associated with a transient risk factor, such as surgery. Calf vein thromboses, if diagnosed, should be treated with anticoagulation for 6–12 weeks.
85

A prospective study followed 570 patients with a first episode of VTE for 2 years after the cessation of oral anticoagulant therapy.
95
The risk of recurrence at 2 years in those who had presented with VTE within 6 weeks of surgery or in pregnancy or postpartum was zero, in contrast to those who had had idiopathic events (19.4%) and those who had had a non-surgical risk factor for VTE (8.8%). Patients with a clear precipitating factor for VTE are at low risk of recurrence once stopping anticoagulation if the underlying risk factor has resolved.

Longer-term anticoagulation after a first idiopathic VTE may be appropriate in patients considered at high risk of recurrent VTE, who are at low risk of bleeding, following an individual assessment of risk factors. As active cancer and anticancer treatment both increase the risk of VTE, consideration should be given to continuing anticoagulation.

 

Key points

• 
The risk of developing VTE increases steadily with age, with 1 in 100 individuals over the age of 80 developing a VTE each year.
• 
Thromboembolism in hospital inpatients is common, developing in over 20% of general surgical patients in the absence of thromboprophylaxis. PE is a well-recognised complication of surgery, and a significant cause of perioperative morbidity and death. There are frequently no signs of DVT prior to the onset of PE.
• 
Patients can be identified to be at risk of VTE both by surgical (i.e. procedural) and patient (i.e. thrombophilia or medical comorbidity) risk factors. Undertaking a risk assessment and using appropriate thromboprophylaxis will reduce the risk of VTE.
• 
Thromboprophylaxis with a combination of mechanical and pharmacological agents is effective in preventing VTE in high-risk surgical patients. Further studies to evaluate the efficacy of newer methods (both pharmacological and mechanical) are needed.
• 
If a diagnosis of VTE is considered, appropriate investigations should be performed. Clinical pretest probability and D-dimer testing are useful in the assessment of outpatients, but have not been validated within the hospital inpatient population. Such patients should have appropriate imaging investigations undertaken. If there is a delay in investigation, therapeutic anticoagulation should be commenced unless the bleeding risks outweigh the potential benefits of anticoagulation.
• 
Anticoagulation is the mainstay of treatment for DVT and PE. If anticoagulation is contraindicated, IVC filter insertion should be considered.
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